The present invention relates generally to collecting laser ablated particles, and more particularly to the filtering of the ablated particles resulting from imaging on a medium with a high energy laser.
In the prepress printing industry, it is well known that a substrate such as a film or printing plate (hereinafter collectively referred to as a xe2x80x9cmediumxe2x80x9d) can have an image transferred thereto by selectively xe2x80x9cburningxe2x80x9d areas of a thermally-sensitive surface of the medium with a high energy laser. This method of imaging is generally referred to as thermal imaging. Typically, the power necessary for such image transfer is attained through the use of a laser light source for emitting the high energy laser beam. The specific chemical makeup of the medium will dictate the required characteristics of the light source which are necessary to adequately burn an image onto the medium. Alternatively, the medium can be manufactured so as to have the appropriate chemical makeup to allow imaging with a light source having predetermined characteristics.
In an internal drum imagesetter or platesetter (hereinafter collectively referred to as an xe2x80x9cimagerxe2x80x9d), a medium is typically positioned on the internal cylindrical surface of the drum prior to imaging. When a laser beam is emitted onto the thermally-sensitive surface of the medium positioned within the imager to form the desired image, laser ablation occurs. Laser ablation refers to the loss or removal of material such as melting or vaporization, due to the application of a high energy laser beam with sufficient energy to expose the medium. The material can effectively explode from the surface of the medium, resulting in ablated particles. Thermal imaging thus generates a gaseous, odorous plume of smoke and dust, which include particulate matter.
Existing filtration systems are designed to collect and filter the ablative particles generated during imaging. However, existing filtration systems have several problems. For example, filtration system may operate improperly for various reasons, such as improper installation of a filtering element, saturation of a filtering element with ablative particles, or the non-operation of the air mover subsystem to specification. Typically the only way to determine when a conventional filtration system is operating improperly is either to periodically inspect the filtering elements and the air mover or to make such inspections when the quality of the imaged media degrades to an unacceptable level due to the accumulation of ablative particles in the imager. Additionally, in conventional filtration systems ablative particles are prone to enter the surrounding environment when a filter, saturated with ablative particles, is removed from the system for replacement. Such emissions can be undesirable whether or not the escaping particles exceed the permissible exposure levels (PEC) at which the particles can become hazardous to humans. Ablative particles may not be properly filtered by conventional filtration systems during operation of the imager if a filter access door or other opening in the filtration system housing is not properly closed or sealed prior to initiating imaging operations. Additionally, conventional ablative particle filtration systems tend to transmit excessive noise to the surrounding environment during operation.
Therefore a need exists for an improved filtration system for ablative particles.
Accordingly, it is an object of the present invention to provide an improved ablative particle filtration technique.
Additional objects, advantages, and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detailed description, as well as by practice of the invention. While the invention is described below with reference to preferred embodiment(s), it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of significant utility.
In accordance with the present invention, a flow system includes an air mover, first stage, and second stage. The respective stages could, for example, be different type, e.g. coarse and fine, filter elements, adsorbent cells, or even mufflers, or some combination thereof. Each filter element is preferably housed in a respective cassette, although this is not mandatory.
The air mover is operable to cause a flow, such as a flow of air and ablative particles created by thermal imaging. For example, the air mover may include a motor and impeller. Advantageously, the air mover creates a negative pressure upstream and a positive pressure downstream of the air mover.
The first stage, which is preferably but not necessarily a filter capable of filtering first size particles, e.g. coarse particles, is disposed upstream of the air mover. The first stage operates on the flow, for example by filtering coarse particles from the flow.
The second stage, which might beneficially be an adsorbent cell or a muffler although this is not mandatory, is disposed downstream of the air mover. The second stage further operates on the flow, for example by removing vapors, odors, smoke and fumes or muffling noise in the flow output from the first stage. It will be recognized that if the second stage were a filter, it would operate on the flow by filtering particles from the flow.
According to another aspect of the invention, a third stage, which is preferably but not necessarily a filter capable of filtering second size particles, e.g. fine particles, which are smaller that the first size particles, is optionally disposed upstream of the air mover and downstream of the first stage. The third stage operates on the flow output from the first stage and outputs the operated on flow. If the third stage is included, the second stage further operates on the flow output from the third stage.
According to still other aspects of the invention, the system preferably includes a housing which houses the first stage, the second stage, the air mover, and optionally the third stage. A plurality of wheels movably support the housing. A brake mechanism locks one of the plurality of wheels to prevent movement of the housing. A latching mechanism is provided to latch the housing to another housing, such as the housing of an imaging unit.
According to still other aspects of the invention, the latching mechanism may include a member protruding from an outer surface of the housing. It may be particularly advantageous in certain implementations for the protruding member to be capable of being inserted into an aperture in an outer surface of the other housing.
In one implementation particularly suitable for thermal imaging, both the imaging unit and the filtration unit include respective latch members. The imaging system latch member can be interconnected with the filtration system latch member to thereby latch the filtration unit to the imaging unit.
In a particularly preferred imaging system implementation, the filtration unit includes a housing having an outer surface from which the latch member protrudes. The housing beneficially houses the first stage, the second stage, the air mover, and optionally the third stage. The filtration unit has a plurality of wheels which movably support the housing. The imaging unit also includes a housing, with an aperture in the outer surface of the housing, allowing the filtration unit latch member to be inserted through the aperture and into the imaging unit latch member to interconnect the first and the second latch members and thereby latch the filtration unit to the imaging unit.